What is the local currency?
Omani Rials (OMR or RO). There are notes for OMR 50, 20, 10, 5 and 1 and Baizas (cents) 500 and 100. Coins are there for Baizas 50, 25, 10 and 5.
The Omani Rial is linked to the USD and whereas exchange bureaus will use different exchange rates, 1 OMR is approximately 2.6 USD. Euro and GBP exchange rates will change and are not fixed.
Should I change money before I go?
Whereas there will be some money exchange offices, it would be advisable to have some money changed either in advance or to change it the airport on arrival.
When bring USD with you, please note that most exchange offices, hotels and banks do not accept notes older than 2009, so assure to bring new notes.
How much should I budget per day for extras?
As water and entrance fees are included, you would need money mostly for meals that are not included, additional snacks you might want to buy on the way, souvenirs and tips. For meals OMR 10 per meal would be usually sufficient.
Is it customary to tip?
There is no standard structure for tipping and whereas it is not expected by all, it will of course be appreciated by the guides, drivers, porters in hotels, restaurant staff etc. if you are happy with the services provided. So more of a European than American approach.
Then for your guide and driver, it is customary, though not compulsory to tip them around £5 a day, this would normally be given at the end of the adventure and is completely up to you and whether you feel they have earned it.